Radial tires have gradually become established in various markets, notably the market for passenger vehicle tires. This success is due in particular to the endurance, comfort and low rolling resistance qualities that radial tires have to offer.
The main parts of a tire are the tread, the sidewalls and the beads. The beads are intended to come into contact with the rim. In a radial tire, each of the main parts of which the tire is made, namely the tread, the sidewalls and the beads, has functions that are clearly separated from one another, and therefore has a well-known specific makeup.
A radial tire is essentially reinforced by a carcass reinforcement comprising at least one carcass ply set at an angle substantially equal to 90° with respect to the circumferential direction of the tire. This carcass reinforcement is surmounted radially on the outside, and under the tread, by reinforcing plies that form a belt.
A cross-ply tire differs from a radial tire in that there are at least two crossed plies set at angles other than 90° with respect to the circumferential direction of the tire. The plies are said to be “crossed” because the angles are of opposite sign from one ply to the next.
For describing embodiments of the invention, the circumferential direction of the tire is defined as the direction in a plane perpendicular to the axis of rotation of the tire and tangential to the tire belt reinforcement.
Since the emergence of radial tires, certain cross-ply tires have also been provided with a belt reinforcement under the tread.
In both these types of tire, the tread, in direct contact with the ground, notably has the function of providing contact with the roadway and needs to adapt to the shape of the ground. The sidewalls for their part absorb the unevennesses of the ground by transmitting the mechanical forces required to support the load of the vehicle and allow it to move.
The belt reinforcement is a reinforcement which, on the one hand, needs to be sufficiently rigid with regard to edge deformations so that the tire can develop the cornering thrust necessary for steering, and transmit torque for traction or for braking and, on the other hand, be very soft in bending, that is to say allow variations in curvature in its plane in order to provide a sufficient area of contact of the tire with the ground.
As a result, the belt reinforcement generally has a composite structure allowing it to offer the required rigidity for a relatively low weight. The belt reinforcement is generally made up of at least two plies set at different angles, comprising reinforcers in the form of cords, coated with rubber. The reinforcer elements are crossed from one ply to the other with respect to the circumferential direction and may or may not be symmetrical with respect to this direction.
The following definitions are used here:                “longitudinal or circumferential direction” is the direction of running of the tire,        “radial direction” is a direction that intersects the axis of rotation of the tire and is perpendicular thereto,        “axial direction” is a direction parallel to the axis of rotation of the tire,        “radially on the inside of” means closer to the axis of rotation,        “radially on the outside of” means further from the axis of rotation,        “equatorial plane or midplane” means a plane perpendicular to the axis of rotation of the tire and which divides the tire into two substantially equal halves,        “transverse direction of the tire” means a direction parallel to the axis of rotation,        “radial or meridian plane” means a plane which contains the axis of rotation of the tire.        
When the wall of a tire is holed by a puncturing object such as a screw or a nail, or “punctured”, tire inflation air may escape through the puncture and the resultant loss in pressure may cause the tire to flatten and the vehicle to stop.
In order to address this problem of punctures, which dates right back to the very start of the use of wheels fitted with pneumatic tires, the usual solution is to stop and replace the affected wheel with a spare wheel.
Other solutions have been conceived of and are available on the market in order to avoid having to use a spare wheel.
Document U.S. Pat. No. 5,916,921 presents an aerosol container containing an aqueous latex emulsion mixed with various products including fibrous products and a propellant gas. If the tire flattens, this container is designed to be fixed to the tire valve and expel the propellant gas and the sealing/repair emulsion into the internal cavity of the tire. The tire is then reinflated, at least partially, the emulsion plugs the puncture and running can be resumed, at a low speed initially in order to distribute the emulsion properly over the entire internal surface of the tire, and then normally.
There are also repair kits, which are offered by certain motor manufacturers in place of a spare wheel. The benefit of that is that it reduces the weight of the car and therefore the fuel consumption thereof and saves space under the floor of the luggage compartment.
Tire repair kits and aerosol cans are only temporary repairs. It is appropriate not to exceed a given speed of around 80 km/h and to have the tire checked or changed quickly.
Tire manufacturers have also proposed tires that are provided on their inner wall or within their structure with a layer of elastic, viscous or pasty products referred to as “self-sealing products”, that are able to seal punctures.
However, the application of these self-sealing products makes it possible to reinforce only the crown region of the tire against punctures. Specifically, these self-sealing products are not applied to the internal surface of the sidewalls because, during running, the centrifugal force which is exerted on the tire does not allow the self-sealing product to remain in its initial location.
Another anti-puncture solution would consist in increasing the thickness of the sidewalls. However, this would cause an increase in mass and have a negative impact on the rolling resistance of the tire.